ANNUAL OF SCIENTIFIC DISCOVERY. 



using it merely as a valve seat, which, when worn, may be readily replaced, 

 and at little cost. 



Heating the Exterior of Steam Cylinders. Tlie Glasgow Practical Mechanics 1 

 Journal gives a well attested case serving to illustrate the utility of the 

 "jacket" formerly used to surround the cylinder with steam. A large 

 engine tried alternately with and without steam in the "jacket" required but 

 twenty pounds pressure to perform in the first named case the same labor as 

 required twenty-five pounds in the second. 



Improved Packing for the Slide Valves of Marine Engines. This improved 

 packing is the invention of Mr. Robert "Waddell, of Liverpool, for several 

 years chief engineer of the Africa, and other vessels of the Cunard line of 

 Atlantic steamers. In these vessels, and generally in the large English steam- 

 ers, the D slide valve is used for supplying the steam to the cylinders ; the 

 interior of the valve between the ports of the cylinder communicates 

 with the boiler, and the steam escapes to the condenser beyond the end 

 of the valve. The valve is ordinarily packed with a single strip of pack- 

 ing at the back opposite each port of the cylinder, to prevent the steam blow- 

 ing through into the condenser ; but with this arrangement, the total pres- 

 sure between the valve and the port faces, on which it slides, varies from 

 nothing to several tons in the large engines at different points of the stroke. 

 The result is an unequal wear of the two edges of the port, which have 

 been worn so much out of level in a single voyage across the Atlantic and 

 back, as to cause serious leakage of steam into the condenser, and much 

 trouble in the repairs. The new plan of packing consists in employing two 

 strips, instead of a single strip, one opposite to each edge of the port, a free 

 communication being maintained between the port and the space between the 

 packings. By this means the valve is perfectly balanced, and the pressure 

 between the rubbing faces is reduced to merely the amount required to 

 preyent the steam blowing through, causing a great reduction in the wear of 

 the faces. The new mode of packing is applicable also to single slide valves, 

 and has been tried for more than a year in the Columbian, with complete 

 success. 



Horizontal Cylinder Engines. The horizontal single cylinder engine is 

 gaining ground in Europe on the double cylinder vertical engine. At one 

 time, the great objection to horizontal engines was the excessively unequal 

 wear of the piston upon the lower side of the cylinder ; but owing to the 

 accuracy with which pistons are now made, the wear and tear upon cylinders 

 is greatly reduced. In France the consumption of coal per horse power, in 

 the most common steam engines, is very low only about three pounds, and 

 the makers of them guarantee that they will not exceed that amount. The 

 steam is used at about 50 Ibs. pressure on the square inch, and is cut off at 

 one-fifth of the stroke ; and, so far as economy of fuel goes, they are equal to 

 an engine with two cylinders, the one for high pressure, and the other for 

 expansion the well known "Wolfe principle. 



New Safety Valve. The following is a description of a new safety valve, 

 recently brought out in England. A small cylinder, occupying the place of 

 the common safety valve, is bolted to the top of the boiler, -ml it has a small 



